This study explores the impact of one of the most important scientific developments of the late 19th c., the germ theory of disease, on popular thinking and behavior in the United States, circa 1870 to 1930. Using a wide range of historical sources, from medical school lecture notes and advice books to patent records and oral histories, the project maps the content of, the methods of popularizing, and the varied responses to changing medical theories of infection. The first section concentrates on the decades roughly from the 1870s to the 1890s, when the germ theory of disease was initially popularized; the second section focuses on the late 1890s to the 1920s, when it informed mass educational campaigns against tuberculosis and other infectious diseases. The research design allows for careful consideration of: the disparities between advice and actual behavior; the persistence of older explanatory frameworks and preventive rituals; and variations in disease experience and health beliefs related to race, class, ethnic, gender, and rural/urban differences. The study demonstrates that many of the beliefs and habits formed in this historical period remain a part of our modern health consciousness, and influence how people understand and act upon information about new infectious diseases such as AIDS. It provides historical insight into the persistent problems inherent in mounting mass publicity campaigns against "killer" diseases, such as developing educational methods that work in a culturally diverse society and raising public consciousness about prevention without causing widespread panic or prejudice toward the afflicted. The finished monograph, which will be submitted to a university press, should interest a diverse audience of historians, health care professionals and policy makers, as well as a general readership concerned about how the experience and understanding of disease affects our culture.